An insight into the interaction between fluid and granular soil based on a resolved CFD-DEM method

Fluid-solid interaction is an essential scientific issue interested many researchers in geological and geotechnical fields, which always holds the key to understanding the meso-mechanism underlying the water-induced geohazards of granular soils such as debris flow, piping erosion, and soil liquefaction. Therefore, this study utilized a resolved coupling method of computational fluid dynamics (CFD) and discrete element method (DEM) to investigate the fluid-solid interaction and its underlying meso mechanics within the granular soils. Three representative cases including single particle free setting, seepage in narrow tubes with dense-packed particles, and one-dimensional consolidation of particle column were implemented to validate the accuracy and efficiency of the resolved CFD-DEM in granular soils. Moreover, the influence of the mesh size and timestep were evaluated in dilute and dense particle systems, respectively. All the numerical results indicated well agreement with the experimental or analytical results reported in literatures. Furthermore, the nonlinear behaviours of the fluid-solid interaction (e.g., wake flow and wall effect) and authentic characteristics at pore scale level were fully depicted in this study. These novel findings provided a deep insight into the meso-mechanics of the complicated fluid-solid interaction within saturated granular soils.